1 Adult identification

The double-spotted leafworm, also known as the dragonfly, is a new insect pest that injure corn. Adult body length 3.6 ~ 4.8mm, width 2 ~ 2.5mm, antenna filament 11 segments, the end of black, length is 2/3 of the body length; compound eye is large, oval; prosthodonial plate width is greater than long, The surface is uplifted and covered with many small engraved points; the scutellum is black and triangular; the echelon fins are lined with fine engraved dots; each eosinophil base half has l nearly circular pale spots, surrounded by black, and pale spots behind Not completely closed, the rear ends of the two wings are rounded. The simple identification method is that adults have two large yellowish spots on the base of each elytra wing, surrounded by black, and the ends of the elytra are yellow.

2 habits

Two-spotted spider mites have certain migratory ability. Adults are more sensitive to light and temperature. At noon, the strong light and high temperature have strong ability to fly and take a large amount of leaves. In the morning to night, the light is weak and the temperature is low, then it flies. Poor strength, small activity, often hiding in the back of the leaves.

3 Damage symptoms

The double-spotted spider mite of the corn occurs mainly in July-September, and the adult leaves are used to injure the corn leaves. The leaves of the light are gauze-like, and the entire leaves of the severe corn are dry. The worms have habits of group habits and tending to tenderness. They often focus on one plant feeding corn leaf meat from top to bottom. The young leaves are bitten into holes. After the middle and lower leaves are damaged, the reticular veins or epidermis are left behind. A small area of ​​irregular white spots has a greater effect on photosynthesis; after the corn has drawn silk, the insect prefers to take anthers and filaments, which affects the normal flowering and pollination of the corn, and it is easy to form rotten grains.

4 The law of occurrence

The two-spotted spider caterpillars of corn occur one generation per year. They lay their eggs spawning under the top soil and hatch in the middle and early May of the following year. The larvae live in the soil and prefer to eat the roots of grass crops or weeds; The weeds lived on the ground and moved into the corn fields. In late July, they entered the period of adulthood and continued to be harmed until September.

The degree of occurrence of the double-spotted spider mite depends on a combination of factors such as the number of insects, climatic conditions, and environmental factors. In the weather conditions of normal years, wintering eggs survive more, and young larvae hatch more and the damage is greater.

4.1 Climate Impact

Mainly determined by the temperature and humidity in July and August, high temperature drying is extremely beneficial to the occurrence of the double-spotted spider mite. When the amount of rainfall is small, it is heavy, and when the rainfall is large, the occurrence of light rainfall is extremely unfavorable.

4.2 Environmental Factors

The layout of crop varieties is monotonous, and large-area continuous cropping is implemented, and measures such as dense planting of high-fertilizer and water are generally adopted, which are favorable to the accumulation of corn pests and diseases. Extensive management and weeds on the roadside and field side provide a good ecological environment for the spawning and breeding of insect pests. In addition, the degree of occurrence is also related to the soil, which occurs early in the clay field and causes serious harm, and it is significantly lighter in sandy soil and sandy land. In addition, because of relatively poor production conditions in the hilly areas, there are many droughts and weeds.

5 Comprehensive prevention and control

According to the law of occurrence and living habits of the double-spotted spider mite in the corn field, comprehensive measures such as agricultural control, biological control, and chemical control can be taken.

5.1 Agricultural Prevention and Control

One is to remove weeds from fields, landsides, and canals in a timely manner to reduce the overwintering host plants of the double-spotted spider mite. Second is to timely supplement fertilizers to the farmland after prevention and control of the double-spotted spider mite to promote vegetative growth of crops. And reproductive growth.

5.2 Biological Control

Protect and use natural enemies (such as ladybugs, spiders, etc.).

5.3 Chemical Control

Due to the complex wintering sites of the worm, the principle of “first administer field outside and then field later” should be followed in the prevention and control strategy. Adults should be controlled to prevent and control adult worms that have just been emerged from the host plants such as the edge of the field, land, and channel; Should be used before the adult, you can use pyrethroids, such as 2.5% lambda 1500 times, or 50% phoxim EC 1500 times spray, the agent should focus on spraying around the ear Spraying time should avoid corn flowering time, so as not to affect pollination; Because pests have the ability to fly, we must strengthen the unified defense rule by region, so as to achieve better control effect.

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